The present invention relates generally to methods and apparatus for taking dimensional measurements of objects and, more specifically, to a method and apparatus for ascertaining three-dimensional measurements and/or volume of objects and methods of use and calibration of same.
Millions of packages per year are handled and shipped by United Parcel Service, Federal Express, and many other smaller courier and delivery services. These packages originate with federal, state, and local governments as well as private businesses of all sizes. In many instances, the charges by the carriers to their customers are based on the so-called "dim-weight factor" or "dimensional weight factor" (DWF) of the article being shipped, a fictitious dimension based on length (L) times width (W) times height (H) in inches divided by a standard agency or association-recognized divisor or conversion factor, commonly 166 (L.times.W.times.H.div.166). The "166" divisor or conversion factor has been recognized and adopted by the International Air Transport Association (I.A.T.A). Even if an object or package is of irregular configuration, the dim weight, using the longest measurement each of length, width, and height, is still utilized for billing purposes. The volume computed by multiplication of object length times width times height may hereinafter be termed the "cubic volume," "spatial volume," or simply the "cube" of the object.
The measurements of the articles shipped are also critical so that the carrier can accurately determine the number of trucks, trailers, or other vehicles which will be required to transport goods to their destinations and so both customers and carriers can accurately estimate their warehousing and other storage needs.
In addition, article weight and measurements are also used to determine and predict weight and balance for transport vehicles and aircraft and to dictate the loading sequence for objects by weight and dimensions for maximum safety and efficiency.
Further, if orders of any items are to be packed into boxes, knowledge of object weight and dimensions would be useful for selecting box size and durability.
To date, it has been a common practice for the customer to manually "cube" or measure boxes or other articles with a ruler, yardstick, or other straightedge marked with units of length, generally inches, perform a calculation for "dim weight," and provide same to the carrier with the package. If the customer does not "cube" the articles, then the carrier performs the operation. Since these measurements and calculations are generally done hurriedly, there is an equal chance that the customer will be undercharged or overcharged. To add to the problem, there are many packages and other objects not susceptible to even a grossly accurate manual measurement of dim weight, for example and not by way of limitation, loaded pallets, tubes, drums, reels of hose, cable or wire, etc. Many machine and automotive parts are shipped "naked" with tags attached or, at most, bagged or shrink wrapped. It is obvious to one skilled in the art that a straightedge measurement to ascertain the greatest extent of each dimension will not be accurate in any of these instances to any degree whatsoever.
It is known to the inventors that a "jig"-type measuring system for packages has been used, with a base and two sides joining in a corner at 90.degree. angles, each marked with gross dimensional units (to the nearest one inch) so that a cubic package can be placed on the base at the corner and measurements taken manually by looking at the markings and recording same, but again, the accuracy is limited by the care and eyesight of the measurer, and the time utilized is unreasonably long when thousands of packages are being shipped, as with Sears, K-Mart, or other large retailers.
In short, a quick, accurate means and method for determining the dimensions and the cubic volume or spatial volume of packages and other objects in a commercial or industrial setting have been lacking for many situations.
U.S. Pat. No. 5,042,015, assigned to the assignee of the present application, discloses practical and commercially successful means and methods for such object measuring of both stationary and moving objects, although the apparatus of the '015 patent requires that moving objects be aligned with the path of movement.
U.S. Pat. No. 5,105,392, assigned to the assignee of the present application, provides alternatives and improvements to the system of the '015 patent. The '392 patent discloses and claims a method and apparatus for three-dimensional measurement of large and irregular objects, such as palletized loads. The '392 patent also discloses and claims a method and apparatus for determining the actual length and width dimensions of randomly-aligned, linearly moving, rectangular objects by determining apparent length, apparent width, and the distance between an object corner facing to the side of the travel direction and the trailing edge of the object. These measurements were then employed to determine the actual object length and width via trigonometrically-based mathematical equations.
The methodology for moving object measurement as described in the '392 patent has been proven to be sound, as have the mathematical relationships, and has also been applied in U.S. Pat. No. 5,220,536, assigned to the assignee of the present application. The '536 patent discloses and claims a method and apparatus for determining the length, width and height of randomly-aligned packages and other substantially rectangular objects by utilization of a combination of a light curtain and an ultrasonic distance sensor.
U.S. Pat. No. 5,422,861, assigned to the assignee of the present application, discloses an object location or detection system for proper placement of an object to be measured on the platen or other object support surface of a measuring system, the use of wave guides as standoffs and received-wave isolators for reflected-wave sensors, and also an improved autocalibration method for ultrasonic sensors.
While the apparatus and methods of the foregoing patents and application have been extremely successful in the market and have, in fact, created an unprecedented commercial and industrial demand for dimensional measurement, these advances have also pointed toward a need for some refinements which may further enhance their utility and accuracy.
For example, while the apparatus and method of these patents and applications have addressed most customer requirements for accurate and rapid dimensional measurement with attendant weighing capability, certain industries such as the pharmaceutical, publishing and electronic component industries desire higher precision due to the relatively small (for example, under six inches per dimension) dimensions and weight (for example, under one pound) of the containers and packages they employ. While it is possible under certain conditions to provide such precision with state-of-the-art reflected-wave ultrasonic sensors, this cannot be assured under all operating conditions. Similarly, the design of current, commercially available, stationary, combined dimensioning and weighing systems, wherein the sensor supports are part of the same assembly as the platen on which the parcel to be measured rests, adds substantial weight to the zero or tare setting before placement of the parcel or other object to be measured and weighed. This design reduces the sensitivity obtainable using a compact, reasonably priced load cell and platen support assembly.
U.S. Pat. No. 5,606,534 and continuation application Ser. No. 08/798,569 filed Feb. 11, 1997, disclose and claim laser-based dimensioning systems for stationary and in-motion applications. One preferred embodiment of the invention of the '534 patent comprises a static or stationary measurement unit, wherein three emitter-receiver laser sensor units are supported on a sensor support assembly in mutually perpendicular orientation and aimed toward a common point. The parcel or other object to be measured is placed on a horizontal platen supported by a load cell or other suitable weighing device, the platen being isolated from the sensor support assembly for greater sensitivity and accuracy in weight determination.
In operation, the three laser sensor units are fired sequentially to prevent interference between reflected light, each laser beam being reflected from a side of the parcel and reflected non-specularly, the reflection being focused through a lens and ambient light filter associated with the receiver unit, which preferably includes a transversely-extending charge-coupled device (CCD) linear image sensor. The distance between the face of a sensor unit and the side of the parcel at which it is aimed affects the angle of reflection of the laser beam, and thus the location of the focused, filtered, reflected beam on the image sensor. Pixel locations on the CCD can be correlated to sensor-to-object distances via a curve fit and linear fifth-order polynomial equation, or via a look-up table. Thus, since the distance is known between each sensor unit and a zero point at which the far corner of the parcel is located, each dimension of the parcel may be readily ascertained by subtracting the known distance from the sensor-to-object distance.
A second preferred embodiment of the invention of the '534 patent comprises a dynamic or in-motion dimensioning system which uses at least one, and preferably two, emitter-receiver laser sensor units as previously described, one placed to each side of the path of movement of an object moving linearly at a known constant rate, to measure the length and width of the object. The height of the object may be measured by a third, downwardly-facing laser sensor unit suspended over the object's path or by other means known in the art, such as a light curtain or ultrasonic sensor, if the object is cuboidal. The in-motion dimensioning system as desired may be used, as with the stationary embodiment, to measure dimensions and volume of cuboidal objects as well as the gross or spatial volume of other, irregular objects. However, the in-motion system also possesses the capability to determine the actual outline of objects of irregular shape, since repeated sampling of the distances between the sensor units and a moving object will produce a scan of the outline or footprint of the object. Further, if desired, more than one downwardly-facing sensor may be employed, and the sensors placed at a non-perpendicular orientation to the object path, so as to provide the capability of better definition of the object volume outline being scanned.